How Long Will A 100 LB Propane Tank Last For Heating?

Heather Robbins
by Heather Robbins
A 100 lb tank of propane sounds massive, but gauging how long it will last for heating purposes is tricky. Several factors determine how long it will last, such as the power of the heating system. Follow along as we explore the factors that affect how long your 100 lb propane tank will last.

Using propane as a fuel source for heat offers the sense of ambiance and warmth that a fireplace provides, except without the mess of charred wood and ashes. Most homeowners prefer to have a 100-pound propane tank since it lasts longer than the smaller tanks. But, how long will a 100-pound propane tank last when used for heating?

A 100-pound propane tank holds 23.6 pounds of propane when it’s full. If your fireplace is 20,000 BTU and you use it 12 hours a day, the 100-gallon propane tank will last you around 9 days. With continuous operation around the clock, it will last about 4.5 days, give or take.

Knowing how long a 100-pound propane tank lasts when used for heating is essential, especially during the winter months. This can help you be prepared, even for worst-case scenarios. In this article, we will show you how to calculate your fuel correctly.

Related Content: How To Tell How Much Propane Is Left In A 100-lb Tank | How Much Propane Does It Take To Heat A 2000 Square Foot Home? | Is It Cheaper To Heat A Home With Propane Or Electricity?

Calculating Your Propane For Heating

First, you will need to find the label for your fireplace burner to check for the BTUs or British Thermal Units that it uses per hour. You can also ask the dealer from which you bought your fireplace. You will need this information for your calculations.

Now, your propane, or LP gas, is sold by the pound or by the gallon. So, you must convert the BTU usage into either gallons of propane or pounds of propane for each hour that your fireplace is used.

For instance, a 100-pound propane tank has a capacity of 2,160,509 BTUs. If your fireplace is 20,000 BTUs, you will need to divide 2,160,509 by 20,000 to get the hourly burn rate. This equals out to be about 108 hours. Then, divide the number of hours by the hours used. For instance, if you plan to use your heater 24 hours a day, this will provide you with four days of heat. If you use it for 12 hours per day, it will last about nine days.

How Big Is A 100-Pound Propane Tank?

The 100-pound propane tank is the largest portable tank that you can have. It weighs about 70 pounds when it is empty and holds 100 pounds of propane, or 24 gallons liquified. When it’s full, the tank weighs about 171 pounds. It stands at about 46.5 inches tall with a 15-inch diameter.

Calculating Your Consumption Rate

How long your 100-pound propane tank lasts depends on the rate at which your fireplace consumes the propane, as well as how often you use it. For instance, one gallon of propane will provide about 91,500 BTUs. This amount of propane weighs about 4 ¼ pounds, which equals to around 21,500 BTUs per pound.

So, if your fireplace runs at 26,000 BTUs per hour, then you will burn one pound of propane in about 50 minutes. This will equate to about 3.5 hours of burn time for each gallon of propane.

Which Size Of Propane Tank Should You Use?

The size of the propane tank you use depends on what exactly you’re using propane for. If you’re only using your propane for heating, then a 100-pound tank is perfect for that. However, it’s not ideal if you’re using your tank for other appliances as well.
Here are several choices you have for propane tank sizes:

  • 120 -325 gallons
  • 500 gallons
  • 1000 gallons
  • 1450 – 1990 gallons

What you choose also depends on the amount of room you have in your yard and whether you’re open to having an underground tank or if you want to keep the tank above ground.

120 To 325 Gallon Tank

The 120-to-325-gallon tanks are great if you’re only using a few propane appliances. For example, if you’re using propane for your gas fireplace, the hot water tank, and your stove, then this size of propane tank is perfect for what you need it for.

500 Gallon Tank

If your heater is meant to produce heat for your entire home rather than just for a room, and you also use your propane for multiple household appliances, then a 500-gallon tank will fit your needs perfectly. This helps so that you don’t need to fill the tank up quite as much and is great for heating a smaller home.

1000 Gallon Tank

A tank of this size is excellent for anyone who uses a large amount of propane throughout the year. If your home is larger with multiple stories you need to heat, then this would be the right choice for you. You can heat your entire house and use propane ran appliances with on issues on a 1,000-gallon tank.

1450 To 1990 Gallon Tank

Usually, you don’t need a tank that’s larger than 1,000 gallons for use on a residential property. However, if you have an extremely large home or two homes running from the same propane tank, and you use propane for all appliances and heating, this may be something you want.

Cost Of Propane Tanks

Knowing the cost of propane tanks is essential, especially if you’ve decided it would be in your best interest to purchase a larger propane tank. Below we’ve included a table that shows the estimated costs.

Tank Size (Gallons)

Cost For Tank


$30 – $60


$350 – $700


$400 – $800


$400 – $800


$500 – $1,000


$500 – $3,000


$1,500 – $3,500

Over 1000

$1,700 – $5,000

Cost To Fill Your Propane Tank

The cost for you to fill your propane tank will of course depend on how large your tank is.

Tank Size (Gallons)

Fill Cost


$15 – $25


$150 – $250


$300 – $500


$360 – $600


$750 – $1,250


$1,500 – $2,500


$3,000 – $5,000

Over 1000

$3,500 – $7,000

Propane typically costs about $3 to $5 per gallon, according to the national average. However, these prices will go down if you find a good deal. For example, if you have a 1,000-gallon tank, sometimes businesses will give you a 20% discount upon refill, which will then cost you about $2,400 to $4,000 instead of $3,000 to $5,000.

Don’t Let The Fill Price Phase You

While it can be a bit overwhelming to pay $3,000 to fill your tank, you need to understand that a 1,000-gallon tank will last you anywhere between one year and two years, depending on the rate of consumption. $3,000 for a year’s worth of fuel is nothing compared to the amount of money you will pay for electricity and heating within that period.

Not to mention, the above prices are based on worst-case scenarios. It’s better to be surprised by unexpected savings on the price of something rather than unforeseen costs.

Related Questions

How often does a 100 lb propane tank need to be recertified?
A 100-pound propane tank needs to be certified at least every 12 years. That goes for any tank that is 100 pounds or less, as they expire 12 years from the manufacturing date. Once it reaches the expiry date, you have two choices: Exchange the tank for a new one, or get it inspected so that you can requalify it for use for another five years.
How old can a propane tank be to refill?
A propane tank can be no longer than 12 years old if you want to have it refilled. If it’s expired, then you will need to bring it in to have it recertified, or you will need to exchange it for a new tank.
How can you tell how much propane is left in a 100-pound tank?

The easiest way to tell how much propane you have left in your tank is by feeling the tank. First, you will need to pour warm water on it and then rub your hand on the side. When you find the propane level, the temperature will be cooler to the touch. You can mark on the outside where the level is, and also write the date so you can track it.

Wrapping It Up

The amount of time that a 100-pound propane tank will last you depends on how many BTUs your gas fireplace is, as well as the rate at which you consume your propane. A higher BTU unit will burn through propane more quickly than one that runs lower BTUs. Also, if you’re running your heater 24 hours a day instead of 12 hours per day, you can expect to burn through more propane.

If you are using propane for more than just your heat, it might be worth looking into purchasing a larger tank. That way, you only have to track one tank instead of multiple ones. Plus, you won’t need to pay for refills as much. Usually, if you have a larger tank, companies will give you a deduction on buying propane in bulk, which will save you money in the long run.

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Heather Robbins
Heather Robbins

Heather is a passionate writer who loves anything DIY. Growing up, she learned everything from home repairs to design, and wants to share her tips with you. When she's not writing, she's usually hiking or searching for her next DIY project.

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